Vanadium-containing petroleum fuels modified with rare earth and alkali metal additives



Oct. 9, 1962 A. G. ROCCHINI ETAL VANADIUM-CONTAINING PETROLEUM FUELS MODIFIED WITH Filed June 14, 1960 RARE EARTH AND ALKALI METAL ADDITIVES 2 Sheets-Sheet 1 Oct. `9, 1962 A. G. RoccHlNl ETAL 3,057,151

VANADIUM-CONTAINING PETROLEUM FUELS MODIFIED WITH RARE EARTH AND ALKALI METAL ADDITIVES 2 Sheets-Sheet 2 Filed June 14, 1960 w w m N o y u a o o wzgzzoo znowlr ME l D d @Q IE5 MEE .QON 0 4 N n ,oom .cov m2922528 5558-515 o u .oom M zmrnz IEE NEE X mzmz 235cm o n 'Nl 'OS/'9W NI SSO'I '.LM NOISOHHOO INVENTORS. ALBERT G. ROCCHINI CHARLES E. TRAUTMAN BY ite ware

Filed .lune 14, 1960, Ser. No. 36,095 8 Claims. (Cl. 60-39.02)

This invention relates to vanadium-containing petroleum fuels. More particularly, it is concerned with rendering non-corrosive those residual fuels which contain such an amount of vanadium as normally to yield a corrosive vanadium-containing ash upon combustion.

This application is a continuation-impart of our prior copending application, Serial No. 701,842, filed December l0, 1957, now abandoned, and assigned to the same assignee as the present application.

It has been observed that when a residual type fuel oil containing substantial amounts of vanadium is burned in furnaces, boilers and gas turbines, the ash resulting from combustion of the fuel oil is highly corrosive to matelials of construction at elevated temperatures and attacks such parts as boiler tubes, hangers, turbine blades, and the like. These effects are particularly noticeable in gas turbines. Large gas turbines lshow promise of becoming an important type of industrial prime mover. However, economic considerations based on the efficiency of the gas turbine dictate the use of a fuel for this purpose which is cheaper than a distillate diesel fuel; otherwise, other forms of power such as diesel engines become competitive -with gas turbines.

One of the main problems arising in the use of residual fuel oils in gas turbines is the corrosiveness induced by those residual fuel-s containing suicient amounts of vanadium to cause corrosion. Where no vanadium is present or the amount of vanadium is small, no appreciable corrosion is encountered. While many residual fuel oils as normally obtained in the refinery contain so little vanadium, or none, as to present no corrosion problems, such non-corrosive fuel oils are not always available at the point where the oil is to be used. In such instance, the cost of transportation of the non-corrosive oil to the point of use is often prohibitive, and the residual oil loses its competitive advantage. These factors appear to militate against the extensive use of residual fuel oils for gas turbines. Aside from corrosion, the formation of deposits upon the `burning of a residual fuel in a gas turbine may result in unbalance of the turbine blade-s, clogging of openings and reduced thermal efficiency of the turbine.

Substantially identical problems are encountered when using a solid residual petroleum fuel containing substantial amounts of vanadium. These fuels are petroleum residues obtained by known methods of petroleum refining such as deep vacuum reduction of asphaltic Acrudes to obtain solid residues, visbreaking of liquid distillation bottoms followed by distillation to obtain solid residues, coking of liquid distillation bottoms, and the like. The solid residues thus obtained are known variously as petroleum pitches or cokes and find use as fuels. Since the vanadium content of the original crude oil tends -to concentrate in the residual fractions, and since the processing of the residual fractions to solid residues results in further concentration of the vanadium in the solid residues, the vanadium corrosion problem tends to be. intensified in using the solid residues as fuel.

States Patent Dice The vanadium-containing ash present in the hot flue gas obtained from the burning of a residual fuel containing substantial amounts -of vanadium compounds causes catastrophic corrosion of the turbine blades and other metal parts in a gas turbine. The `corrosive nature of the ash appears to be due to its vanadium oxide content. Certain inorganic compounds of vanadium, such as vanadium `oxide (V205), which are formed on combustion of a residual fuel oil containing vanadium compounds, vigorously `attack various metals, their alloys, `and other materials at the elevated temperatures encountered in the combustion gases, the rate of attack becoming progressively more severe as the temperature is increased. The vanadium-containing ash forms deposits on the parts affected and corrosively reacts with them. It is a hard, adherent material when `cooled to ordinary temperatures.

It has already been proposed to employ in corrosive residual fuels small amounts of certain metal compounds to mitigate the vanadium corrosion. Such compounds are of varying effectiveness and it has not always been possible to reduce vanadium induced corrosion to a minimum amount.

It has now been discovered that residual petroleum fuels containing vanadium in an amount sufficient to yield a corrosive vanadium-containing ash upon combustion can be rendered substantially non-corrosive by incorporating therein to form a uniform blend an amount of an oilsoluble or oil-dispersible rare earth metal salt of an acidic organic compound yielding about 0.25 to 0.375 atom weight of rare earth metal per atom weight of vanadium in said fuel, and an amount of `an oil-soluble or oildispersible alkali metal salt of an acidic organic compound yielding about 0.25 to 0.375 atom weight of alkali meta-l per atom weight of vanadium in the fuel, the tot-a1 amount of rare earth metal and alkali metal ranging from about 0.5 to 0.75 atom weight per atom weight of vanadium. In the fuel compositions of the invention, the coaction of the two `additive compounds is such that the corrosion is reduced to negligible amounts.

In the accompanying drawings:

FIG. l shows an `apparatus for testing the corrosivity of residual fuel oil compositions; and

FIG. 2 shows in graphic form the individual effects and combined effects of certain of the described additives in retarding corrosion.

The type of residual fuel oils to which the invention is directed is exemplified by No. 5, No. 6 and Bunker C fuel oils which contain a sufficient amount `of vanadium to form a corrosive ash upon combustion. These are residual type fuel oils obtained from petroleum by methods known to the art. For example, residual fuel oils are obtained as liquid residua by the conventional distillation of total crudes, by atmospheric and vacuum reduction of total crudes, by the thermal cracking of topped erudes, by visbreaking heavy petroleum residua, `and other conventional treatments of heavy petroleum oils. Residua thus `obtained are sometimes diluted with distillate fuel oil stocks, known as cutter stocks, and the invention lalso includes residual fuel oils so obtained, provided that such oils contain sufficient vanadium normally to exhibit the corrosion characteristics described herein. It should be understood that ldistillate fuel loils themselves contain :either no vanadium or such small amounts as to present no problem of corrosion. The total `ash from commercial residual fuel oils usually ranges from about 0.02 to 0.2 percent by weight. The vanadium pentoxide (V205) content of such ashes ranges from zero to trace amounts up to about percent by weight for low vanadium stocks, exhibiting no significant vanadium corrosion problem, to as much as 85 percent by weight for some of the high vanadium stocks, exhibiting severe corrosion.

The type of vanadium-containing solid residual fuels to which the invention is directed is exemplied by the coke obtained in known manner by the delayed thermal coking or uidized coking of topped or reduced crude oils and by the pitches obtained in known manner by the deep vacuum reduction of asphaltic crudes to obtain solid residues. These materials have ash contents of the order of 0.18 percent by Weight, more or less, and contain corrosive amounts of vanadium when prepared from stocks contain- 'ing substantial amounts of vanadium. A typical pitch 'exhibiting corrosive characteristic-s upon combustion has a softening point of 347 F. and a vanadium content, as vanadium, of 578 parts per million.

The alkali metal and rare earth metal salts of the invention are prepared in known manner lfrom any oil- Vsoluble: or oil-dispersible acidic organic compound that forms oil-soluble or oil-dispersible metal salts. Representative examples of the `salts of the invention include 'oil-soluble and oil-dispersible alkali metal and rare earth metal salts of: (l) the fatty acids, eg., valerie, caproic, v2-ethylhexanoic, oleic, palmitic, stearic, linoleic, tall oil and the like; (2) alkylaryl sufonic acids, e.g., oil-soluble petroleum sulfonic acids and dodecylbenzene sulfonic acid; (3) long chain alkylsulfuric acids, eg., lauryl sulfuric acid; (4) petroleum naphthenic acids; (5) rosin and hydrogenated rosin; (6) al-kyl phenols, eg., iso octyl phenol, t-butylphenol and the like; (7) alkyl phenol sulfides, eg., 'bi s(isooctyl phenol)monosuliide, bis(tbutyl phenol)di sulfide and the like; (8) the acids obtained by the oxidation of petroleum waxes and other petroleum fractions; and (9) oil-soluble phenol-formaldehyde resins, e.g., the Amberols, such as t-butylphenol-formaldehyde resin and the like. Since the salts or soaps of such acidic organic compounds as the fatty acids, petroleum naphthenic acids and rosins are easily prepared, these are preferred materials.

The requirement for oil-solubility or oil-dispersibility of the salts of the invention is to insure uniform blending thereof when employed with a residual fuel. It would obviously be undesirable for the bulk of the additiv to be vconcentrated in a small portion of the fuel while the remainder contained little or no additives. The requirement for uniform blending of the salts is therefore satisfied by the 'use of oil-soluble or oil-dispersible compounds. A-s will be apparent to those skilled in the art, the distinction between oil-solubility `and loil-dispersibility is a matter of degree, it being sufficient for present purposes that a fairly stable dispersion of the dispersible additives be obtained, or that redispersion of a settled additive be easily accomplished by simple agitation.

The alkali metal salts of the invention include sodium, potassium, lithium, rubidium and cesium salts. Because of their low cost and suitability for the purposes of the invention, the sodium and potassium salts are preferred. Particularly preferred are sodium or potassium naphthenates, tallates (tall oil soaps) and rosinates.

The rare earth metal salts of the invention include the salts of the rare earth elements, that is, the elements of atomic numbers 57 to 71, inclusive. The rare earth elements include lanthanum, cerium, praseodymium, neodymium, samarium, europ-lum, gadolinium, terbium, dysyprosium holmium, erbium, thulium, ytterbium and lutecium.

Commercial ores of the rare earth elements are primarily monazite and bastnasite. Monazite is an orthophosphate of the rare earth elements and thorium. Bastnasite is la cerium earth uorocarbonate. Generally the ores are opened by heating with sulfuric acid, the thorium is separated in the case of the monazite ore and the rare earths are then isolated either by precipitation as oxalates or by precipitation with sodium sulfate to form an insolu- 'ble double rare earth sodium sulfate, all in accordance With known methods. The following table shows the composition of rare earths in typical commercial rare earth salts.

As the above table shows, the rare earth elements are initially obtained by commercial processing methods as mixtures. Such mixtures of rare earth elements in the form of salts of acidic organic compounds are particularly useful in the practice of this invention. Although the individual rare earth metal salts can successfully be employed, compounds of the individual elements are more expensive because of the increasing diiculty of further separating individual elements. The rare earth metal salts of acidic organic compounds are prepared in known manner Iby reaction of the rare earth oxides or carbonates with an acidic organic compound or by metathesis of a rare earth nitrate or other salt with an alkali metal salt of an acidic organic compound. The naphthenates, tallates and rosinates of the rare earth metals are preferred additives.

In the practice of the invention with vanadium-containing residual fuel oils, the oil-soluble or oil-dispersible salts of the invention are uniformly blended with the oil in the disclosed proportions. Since, on Va weight basis in relation to the fuel, the amounts of the additives are small, it

-is desirable to prepare concentrated solutions or dispersions of the additives in a nap-htha, kerosene or gas oil for co-nvenience in compounding.

In the practice of the invention with solid residual fuels, incorporation of the additives of the invention is accomplished in several ways. The additives can be dissolved or dispersed in the liquid vanadium-containing residual stocks or crude oil stocks from which the solid residual fuels lof the invention are derived, and the mixture can then be subjected to the refining process which will produce the solid fuel. For example, in the production of a pitch by the deep vacuum reduction `of an asphaltic crude oil, sodium naphthenate and rare earth naphthenate are mixed with the oil in the disclosed proportions, and the whole subjected to deep lvacuum reduction to obtain a pitch containing the additives uniformly dispersed therein. As still another alternative, particularly with a pitch which is Withdrawn in molten form from the processing vessel, the additives can be mixed with the molten pitch and the mixture allowed to solidify after which it is ground to the desired size.

In the case of either liquid or solid residual fuels, the additives can be separately fed into the burner as concentrated solutions or dispersions. In such a case, it is pref ferred to meter the additives into the fuel line just prior to the combustion zone. In a gas turbine plant where the heat resisting metallic parts are exposed to hot combustion gases at temperatures of the order of 1200 F. and above, the additives can be added separately from the fuel either prior to or during combustion itself, or even subsequent to combustion. However they may specifically be added, Whether in admixture With or separately from the fuel, the additives are introduced into said plant upstream tof the heat resisting metal parts to be protected from corrosion.

It is a characteristic feature of the invention that the use of both the rare earth metal and alkali metal additives in the proportions described and claimed results in an unexpectedly greater reduction in corrosion to lower, substantially minimal amounts than can be obtained by using either the rare earth or alkali metal additives singly in the same total additive content. This unexpected co- J action is obtained when the amounts `of the alkali metal and rare earth metal additives are each in the range of about 0.25 to 0.375 atom weight per atom weight of vanadium in the fuel, the total amount of additive thus being inthe range of about 0.5 to 0.75 atom weight of additive metals per atom weight of vanadium. When the total additive content is less than about 0.5 atom weight corrosion rises rapidly, and when the total additive content is greater than about 0.75 atom weight the reduction in corrosion tends to approach the reduction in corrosion obtained with the same total amount of the rare earth `additive used alone. It is to 'be noted that, when using a mixture of rare earth elements in the rare earth salts, the average atomic weight of the total rare earth elements in the mixture is employed in determining the atom weight ratio of rare earth elements to vanadium in the fuel.

The following specific examples are further illustrative of the invention. In these examples, the sodium naphthenate and rare earth naphthenate are salts of petroleum naphthenic acids and are employed as solutions in petroleum naphtha. The sodium naphthenate contains 6 percent by Weight of sodium and the rare earth naphthenate contains 4 percent by weight lof rare earth metals. This rare earth naphthenate is a mixture of rare earth metal naphthenates, the mixture of rare earth metals being in substantially the same proportion as exists in the rare earth compounds obtained after the separation of thorium from monazite but before separating individual rare earth elements. The oxide analysis `of these rare earth naphthenates is therefore substantially identical with that shown in Table I, supra, for rare earth salts derived from monazite. In determining the atom weight ratio of the rare earth metals in the mixture of rare earth metal naphthenates to the vanadium in the residual fuels, an average rare earth metal atomic weight of 140 is employed.

Example I With a residual fuel `oil uniformly blend 0.415 percent by weight of the above rare earth naphthenate solution and 0.035 percent by weight of the above sodium naphthenate solution. The residual fuel oil employed has the following inspection:

Gravity: API 20.2 Viscosity, Furol: Sec.:

122 F. 25.3 Flash, O.C.: F 240 Fire, O.C.: F 250 Sulfur, B: percent 2.1 Ash: percent 0.04 Vanadium: Ppm. of oil 243 Sodium, Ppm. of oil The resulting composition has an atom weight ratio of sodium to vanadium of 0.25zl and an atom weight ratio of rare earth metals to vanadium of 0.25: l.

Example Il To the same residual fuel oil of Example I add and uniformly blend 0.618 percent of the above rare earth naphthenate solution and 0.045 percent of the above sodium naphthenate solution. The resulting composition has an atom weight ratio of sodium to vanadium of 0.375:1 and an atom weight rratio of rare earth metals to vanadium of 0.375 :1.

Example III Melt a solid petroleum pitch obtained from the deep vacuum reduction of an asphaltic crude. This pitch has a softening point of 347 F. and a vanadium content of 578 parts per million. While the pitch is in molten form, add and uniformly blend therein with stirring 0.125 percent by weight of a solution of sodium rosinate in naphtha containing 1.35 percent by Weight of sodium and 1 percent by weight of a solution of cerium tallate in t8 naphtha containing 4 percent by weight of cerium. Upon cooling and solidification, grind the mixture to about 150 mesh. The resulting fuel has an atom weight ratio, Na:V, `of 0.25 :1, and an atom weight ratio, CezV, of 0.2511.

In order to test the effectiveness `of the additives :of the invention under conditions of burning residual fuels in a gas turbine, the apparatus shown in FIGURE 1 is ernployed. As shown in FIGURE 1, the residual `oil under test is introduced through line 10 into a heating coil 11 disposed in a tank of water 12 maintained at such temperature that the incoming fuel is preheated to a temperature lof approximately 212 F. From the heating coil 11 the preheated oil is passed into an atomizing head designated generally as 13. The preheated oil passes through a passageway 14 into a nozzle 15 which consists of a #26 hypodermic needle of approximately 0.008 inch LD. and 0.018 inch O.D. The tip of the nozzle is ground square and allowed to project slightly through an orifice 16 of approximately 0.020 inch diameter. The orifice is supplied with 65 p.s.i.g. air for atomization of the fuel into the combustion chamber 21. The air is introduced through line 17, preheat coil `18 in tank 12, and air passageways 19 and 20 in the atomizing head 13. The combustion chamber 21 is made up :of two concentric cylinders 22 and 23, respectively, welded to two end plates 24 and 25. Cylinder 22 has a diameter of 2 inches and cylinder 23 has a diameter of 3 inches; the length lof the cylinders between the end plates is 81/2 inches. End plate 24 has a central `opening 26 into which the atomizing head is inserted. End plate 25 has a one (1) inch opening 27 covered by a baiiie plate 28 mounted in front of it to prevent direct blast of flame on the test specimen 29. Opening 27 in end plate 25 discharges into a smaller cylinder 30 having a diameter 4of 11/2 inches and a length of 6 inches. The specimen 29 is mounted near the downstream end `of the cylinder approximately 1% inches from the outlet thereof. `Combustion air is introduced by means of air inlet 31 into the annulus between cylinders 22 and 23, thereby preheating the combustion air, and then through three pairs `of 9%16 inch tangential air inlets 32 in the inner cylinder 22. The first pair of air inlets is spaced 1A inch from the end plate 24; the second pair 5A inch from the first; and the third 3 inches from the second. The additional heating required to bring the combustion products to test temperature is supplied by an electric heating coil 33 surrounding the outer cylinder 23. The entire combustion assembly is surrounded by suitable insulation 34. The test specimen 29 is a metal disc one inch in diameter by 0.125 inch thick, With a hole in the center by means of which the specimen is attached to a tube 35 containing thermocouples. The specimen and tube assembly are mounted ion a suitable stand 36.

In conducting a test in the above-described apparatus, a weighed metal specimen is exposed to the combustion products of a residual fuel oil, the specimen being maintained at a selected test temperature of, for example, 1350", 1450 or 1550 F. by the heat of the combustion products.- The test is usually run for a period lof hours with the rate of fuel feed being 1A; pound per hour and the rate of atomizing air feed being 2 pounds per hour. The combustion air entering through air inlet 311 is fed at 25 pounds per hour. At the end of the test run the specimen is reweighed to determine the weight of deposits and is then descaled with a conventional alkaline descaling salt in molten condition at 475 C. After descaling, the specimen is dipped in 6 N hydrochloric acid containing a conventional pickling inhibitor, and is then washed, dried and weighed. The loss in Weight of the specimen after descaling is the corrosion loss.

Tests are conducted in the apparatus just described using a 25-20 stainless steel as the test specimen. The tests are run for 100 hours at a temperature `of l450 F. under the conditions described above. Tests are made with the fuel oil compositions of Examples I and II, with 7 fuel oil compositions similar to these examples but containing different proportions fof the mixture or :only one of the additives in vvarying amounts, and with the uncompounded residual fuel oil of the examples. The uncompounded Ifuel of Examples I and II showed a corrosion Weight loss of 1143 Ing/sq. in. land deposits amounting to 231 mg./ sq. in. The following tables show the cornosion and deposits obtained.

TABLE II SODIUM ADDITIVES Atom Wt. Corrosion,

Ratio, Wt. Loss of Deposits, Na: V Specimen, Mg./Sq. In.

Mg./Sq. In.

Fuel-i-Sodium Naphthenate 0. 5:1 426 512 D 1:1 110 237 2:1 112 195 3:1 96 121 4:1 99 370 6:1 34 68 TABLE III RARE EARTH ADDITIVES Atom Corrosion W t. Wt. Loss of Deposits, Ratio, Specimen, Mg./Sq. In.

Rare Mg./Sq. In. EarthzV TABLE IV SODIUM AND RARE EARTH (RE) COMBINATIONS Corrosion, Atom Wt. Ratio, Wt. Loss of Deposits, Additive MetalszV Specimen, Mg/Sq. In.

MgJSq. In.

Compounded Fuel of (RE: V=O.25:1)

Example I. {(Na; v=o.25;1 i 48 82 Compounded Fuel oi {(RE:V=0.375:1 l( 15 62 Example II. (Na: V=0.375:1). Fuel-l-Rare Earth Naphthenate -l- (RE: V=0.5:1).. 14 61 Sodium Naphthe- (Na:V=0.5:1) nate [(RE V l) D Navli 1)...i 15 127 The corrosion results for each fuel shown in the above tables was plotted against the total additive content of such fuel, separate curves being `obtained for the sodium aditives alone, the rare earth additives alone and the `combination of sodium and rare earth additives. These curves are shown in FIGURE II.

It will be seen from the .data in the above tables and .the curves of FIGURE II that, over the range of proportions of total additive content `of from about 0.5 to 0.75 atom weight of additive metal per atom weight of Vanadium, the sodium and rare earth additive combinations unexpectedly reduce corrosion to a far greater extent than the same concentration of either the sodium or rare earth additives alone. While the additive combinations 'in amounts less than about 0.5 atom weight of total additive metal per atom weight of vanadium would lseem to possess `an unexpected superiority over the individual additives at the same concentrations, the amount of corrosion with such low concentration combinations would rapidly increase with decreasing additive content. On the other hand, when the additive combinations are `employed in total amounts exceeding about 0.75 atom Weight per atom weight `of vanadium, the amount of corrosion obtained rapidly approaches that of the rare earth additive used alone, las shown in FIGURE II.

It will be understood that the above specic examples are illustrative only, yand are not intended to limit the invention. Other oil-soluble or oil-dispersible rare earth metal salts and alkali metal salts of acidic organic compounds, as disclosed, are successfully employed.

A typical analysis of the 25-20 stainless steel employed in the testing described is shown in the following table in percent by weight:

TABLE V 0.04 Balance Resort `may be had to such modifications and variations as fall within the spirit of the invention and the scope of the appended claims.

We claim:

l. A fuel composition comprising a uniform blend of a major amount of a residual petroleum fuel yielding a corrosive vanadium-containing ash upon combustion, an amount of a salt selected from the class consisting of oilsoluble and oil-dispersible rare earth metal salts of an acidic organic compound yielding about 0.25 to 0.375 atom weight of rare earth metal per atom weight of vanadium in said fuel, and an amount of a salt selected from the class consisting of oil-soluble and oil-dispersible alkali metal salts of an acidic organic compound yielding about 0.25 to 0.375 atom Weight of alkali metal per atom weight of Vanadium in said fuel, the total amount of rare earth metal and alkali metal ranging from about 0.5 to 0.75 atom weight per atom weight of vanadium.

2. The fuel composition of claim 1, wherein the fuel is a solid residual petroleum fuel.

3. The fuel composition of claim 1, wherein the acidic organic compound is selected from the class consisting of -fatty acids, naphthenic acids and rosins.

4. A fuel composition comprising a uniform blend of a major amount of a residual fuel oil yielding a corrosive yvanadium-containing ash upon combustion, an amount of a salt selected from the class consisting of oil-soluble and oil-dispersible -rare earth metal salts of an acidic organic compound yielding about 0.25 to 0.375 atom weight of rare earth metal per atom weight of vanadium in said fuel oil, and an amount of a salt selected from the class consisting of oil-soluble and oil-dispersible sodium salts of an acidic organic compound yielding about 0.25 to 0.375 atom weight of sodium per atom weight of vanadium in said fuel oil, the total amount of rare earth metal and sodium ranging from about 0.5 to 0.75 atom weight per atom weight of vanadium.

5. The fuel composition of claim 4, wherein the rare earth metal salt comprises the mixture of rare earth elements derived from monazite.

6. The fuel composition of claim 5, wherein the acidic organic compound is a naphthenic acid.

7. In a gas turbine plant in which a fuel oil containing vanadium is burned and which includes -heat resisting metallic parts exposed to hot combustion gases and liable to be corroded by the corrosive Vanadium-containing ash resulting from combustion of said oil, the method of reducing said corrosion which comprises introducing into said plant upstream of said parts a mixture of a salt selected from the class consisting of oil-soluble and oildispersible rare earth metal salts of an oragnic acidic compound and a salt selected from the class consisting of oil-soluble and oil-dispersible alkali metal salts of an organic acidic compound, the amount of said rare earth metal salt being suicient to yield about 0.25 to 0.375 atom Weight of rare earth metal per atom Weight of Vanadium in said fuel, and the amount of said alkali metal salt being sulcient to yield about 0.25 to 0.375 References Cited in the file of this patent atom Weight of alkali metal per atom weight of vanadium UNITED STATES PATENTS in said fuel, the total amount of rare earth and alkali metal ranging from about 0.5 to 0.75 atom Weight per 2,949,008 Rocchml et al' Aug 16 1960 atom Weight of vanadium. 5 FOREIGN PATENTS SalisTlogiixlosltof claim 7, Wherem the alkali metal 761,378 Great Britain NOV. 14, 1956 781,581 Great Britain Aug. 21, 1957 1,113,013 France Nov. 23, 1955 1,117,896 France Mar. 5, 1956 

7. 2N A GAS TURBINE PLANT IN WHICH A FUEL OIL CONTAINING VANADIUM IS BURNED AND WHICH INCLUDES HEAT RESISTING METALLIC PARTS EXPOSED TO HOT COMBUSTION GASES AND LIABLE TO BE CORRODED BY THE OCRROSIVE VANADIUM-CONTAINING ASH RESULTING FROM COMBUSTION OF SAID OIL, THE METHOD OF REDUCING SAID CORRSION WHICH COMPRISES INTRODUCING INTO SAID PLANT UPSTREAM OF SAID PARTS A MIXTURE OF A SALT SELECTED FROM THE CLASS CONSISTING OF OIL-SOLUBLE AND OILDISPERSIBLE RARE EARTH METAL SALTS OF AN ORGANIC ACIDIC COMPOUND AND A SALT SELECTED FROM THE CLASS CONSISTING OF OIL-SOLUBLE AND OIL-DISPERSIBLE ALKALI METAL SALTS OF AN ORGANIC ACIDIC COMPOUND, THE AMOUNT OF SAID RARE EARTH METAL SALT BEING SUFFICIENT TO YIELD ABOUT 0.25 TO 0.375 ATOM WEIGHT OF RERE EARTH METAL PERATON WEIGHT OF VANADIUM IN SAID FUEL, AND THE AMOUNT OF SAID ALKALI METAL SALT BEING SUFFICIENT TO YUELD ABOUT 0.25 TO 0.375 ATOM WEIGHT OF AALKALI METAL PER ATOM WEIGHT OF VANADIUM IN SAID FUEL, THE TOTAL AMOUNT OF RATE EARTH AND ALKALI METAL RANGING FROM ABOUT 0.5 TO 0.75 ATOM WEIGHT PER ATOM WEIGHT OF VANADIUM. 